646440 has 32 divisors (see below), whose sum is σ = 1939680. Its totient is φ = 172352.

The previous prime is 646433. The next prime is 646453. The reversal of 646440 is 44646.

646440 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a nialpdrome in base 15.

It is a self number, because there is not a number n which added to its sum of digits gives 646440.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 646440.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2574 + ... + 2813.

It is an arithmetic number, because the mean of its divisors is an integer number (60615).

2⁶⁴⁶⁴⁴⁰ is an apocalyptic number.

646440 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

646440 is an abundant number, since it is smaller than the sum of its proper divisors (1293240).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

646440 is a wasteful number, since it uses less digits than its factorization.

646440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5401 (or 5397 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 24.

The square root of 646440 is about 804.0149252346. The cubic root of 646440 is about 86.4654767730.

Subtracting from 646440 its sum of digits (24), we obtain a square (646416 = 804²).

The spelling of 646440 in words is "six hundred forty-six thousand, four hundred forty".